Involvement of JNK-AP-1 and ERK-NF-κB signaling in tension-stimulated expression of Type i collagen and MMP-1 in human periodontal ligament fibroblasts

Type I collagen (COL I) and matrix metalloproteinase-1 (MMP-1) are the predominant matrix proteins in the extracellular matrix of the human periodontal ligament (PDL). The expression of these proteins in PDL fibroblasts (PLF) is sensitive to physiological and mechanical stress and is critical for PDL remodeling accompanied by alveolar bone remodeling. This study examined how dose tensile force regulates the expression of COL I and MMP-1 and explored the possible roles of mitogenactivated protein kinases (MAPKs) and transcription factors, such as activator protein-1 (AP-1) and nuclear factor-κB (NF-κB). Tensile force stimulated the mRNA expression of COL I and MMP-1 in the cells and also activated MAPKs including extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38 MAPK. A pharmacological inhibitor of ERK or JNK prevented the expression of matrix genes and the nuclear translocation of c-Jun proteins in the force-applied PLF. The knockdown of c-Jun by transfecting the cells with its antisense oligonucleotides reduced the force-induced increase in matrix gene expression. In particular, the ERK inhibitor but not JNK or p38 MAPK inhibitor attenuated the forcemediated stimulation of NF-κB-DNA binding and MMP-1 expression. Overall, these results highlight the mechanotransduction pathways involved in matrix gene expression in PLF, where the tensionstimulated expression of COL I and MMP-1 is controlled by the ERK/JNK-AP-1 and ERK-NF-κB signaling pathways.